1. Technical Field
The present disclosure is directed to a system and method of optically sensing the presence of an object or objects, such as one or more fingers, in a detectable area to perform a text input, such as with a keyboard.
2. Description of the Related Art
Currently, small, light-weight, portable devices, such as smartphones and devices with touch panels are very popular. For these portable devices, there are few easy ways to input text and characters. Some devices include tiny built-in or on board mechanical keyboards or small printed virtual keyboards on the touch panels for typing the characters. Some of the touch panels are included with smartphones and, thus, have a small size. Other touch panels are included on larger devices, such as an iPad or a Kindle, which utilize a much bigger printed keyboard presented on the touch panel. The touch panels are electronic visual displays that can detect the presence and location of a touch within a display area or a screen. Touch panels are common in devices such as game consoles, all-in-one computers, tablet computers, and smartphones.
Although the keyboards are sufficient to input small numbers of characters, such as for a text message, they are not sufficient for inputting longer text, such as more than 200 words. In some instances, the virtual and manual keyboards in smartphones are too small for typing even one character, especially for older people. As a result, there can be many typos by users of such keyboards. On the other hand, virtual keyboards for touch panel devices can occupy almost half of the screen area just to achieve a standard key size.
Virtual keyboards have been proposed to detect text inputs. For example, U.S. Pat. No. 7,215,327 issued to Liu et al. entitled “Device and Method for Generating a Virtual Keyboard/Display,” utilizes two scanning lasers to scan a working surface to determine locations and movements of a user's fingers. The device determines the finger's locations by comparing a time difference received from the two reflected scanning lasers.
Another example, U.S. Pat. No. 6,710,770 issued to Tomasi et al. entitled “Quasi-three-dimensional Method and Apparatus to Detect and Localize Interaction of User-Object and Virtual Transfer Device,” describes a virtual keyboard and virtual input using two optical systems. The first optical system OS1 projects a beam of light parallel to a working surface and the second optical system OS2 receives and detects reflected light from the first optical system, OS1. By using homography, an object's actual location in the real world can be computed from the image pixel coordinate. In order to implement a virtual keyboard, a view angle of the second optical system OS2 would need to be 90 degrees or larger. With such large view angle, the lens distortion can be so significant that the homography transformation can cause huge errors in the computation of the object's real world location. As a result, issues with selection of the correct key can occur.